As is known in the art, Microwave and mm-Wave Monolithic Integrated Circuits (MMICs) and devices must be protected from mechanical damage and degradation due to harsh environments. Such parts are typically mounted in hermetic housings. These housings are comprised of metallic boxes which hold not only the active MMICs but also the substrates upon which they are mounted. Techniques have been proposed to eliminate these metallic housings by using special coatings on the MMICs. Such coatings can be applied at the wafer level and therefore are potentially a low cost alternative to conventional packaging. However, coatings have not yet been shown to provide full environmental protection, nor have they been shown to avoid degradation in the performance of the MMICs in all cases.
An alternative packaging technique involves placement and bonding of air-cavity enclosures made of quartz or other materials, metalized or otherwise, over the individual die. The micro-cover, as is known in the art, results in an increase in the size of the conventional microstrip die since a bonding ring must be allowed in the design. Further, leads which emanate from the MMIC must pass under the cover and be terminated on pads placed on a ledge outside the MMIC active area. The ledge must be sufficiently large to allow access of a bonding tool for assembly.
For microstrip MMIC's designs, the active transistors and tuning elements are placed, along with bonding pads, on the top (epitaxial) surface of the die. Bond wires and associated bonding pads within a conventional housing result in an increase in the size of the MMIC as well as an increase in the cost and complexity of the substrates to which they are mounted. In prior art, techniques have been proposed to reduce or eliminate the bond wires by providing through-via connections from the front surface of a MMIC to the back surface. This technique is sometimes referred to as “Through-Wafer-Interconnect”, “Hot-Via” or “Direct-Backside-Interconnect”. Hot-via designs allow for smaller die and smaller substrates and hence smaller module footprints. Hot-via designs make it easier to route wiring on the MMIC since connection need not be made at the edges of the chip.
A further issue relating to the use of MMIC's within modules along with other components relates to tuning effects due to module walls and nearby components.
It is know in the art that a combination of Hot-Via and Micropackage designs can produce a leadless, hermetically sealed micro-package. The micro-cover is used to hermetically seal the MMIC. The MMIC itself forms the bottom of the package while all of the interconnections are made by the hot-via approach. Thus no leads or bonding pads are needed anywhere on the chip. The need for a ledge is eliminated and a hermetic package is produced thereby reducing the chip size.
In accordance with the invention, a method is provided for packaging a semiconductor device. The method includes: providing a dielectric layer over the semiconductor device; determining patterns and placement of material on the dielectric layer to provide a predetermined magnetic or electric effect for the device, such effects being provided on the device from such patterned and placed material solely by electrical or magnetic waves coupled between such material and the device; and forming the material in the determined patterns and placement to provide the predetermined effects.
In one embodiment, the method includes: mounting a rigid dielectric layer over the semiconductor device, such rigid material being suspended over the device; determining patterns and placement of materials on the dielectric layer to provide a predetermined magnetic or electric shielding for the device; depositing the material, including resistive, metallic, dielectric, magnetic material or any combination thereof, on the rigid dielectric layer; and patterning the deposited material to provide the predetermined shielding.
In one embodiment, a method for packaging a plurality of semiconductor devices formed in a surface portion of a semiconductor wafer, each one of a plurality of regions within the wafer having one of the semiconductor devices therein, such method comprising: providing a dielectric layer over the wafer; depositing a material on the dielectric layer, such material effecting electromagnetic fields on each one of the devices; separating each one of the devices within the wafer.
In accordance with one embodiment, a method is provided for reducing or eliminating electromagnetic interactions between the MMIC and the external environment within a module enclosure. The method involves forming metallic, dielectric or magnetic material structures on the inside and/or outside surfaces of the cover. These structures terminate radiated fields in a known and predictable manner thereby providing shielding and/or feedback reduction to the MMIC.
In accordance with one embodiment, a method is provided for packaging a semiconductor device. The method includes: designing a microwave integrated circuit for the package; creating a computer model of selected package with the designed microwave integrated circuit therein for electromagnetic simulations; generating simulations with the created computer model without electromagnetic structures to define a baseline performance; applying a plurality of different electromagnetic structures to the created model; performing a simulation for each one of the plurality of different electromagnetic structures measuring one of more of the following performance factors: gain, RF emission, feedback gain ripple; and comparing the simulated performance with the baseline performance; and; selecting one of the plurality of different electromagnetic structures.
In one embodiment, the structures for the package include resistive, metallic, magnetic or dielectric material.
In one embodiment, a package for a semiconductor device is provided comprising: a dielectric layer disposed over the semiconductor device; and magnetic material disposed on selected regions of the rigid dielectric layer.
In one embodiment, the dielectric layer is a rigid dielectric layer suspended over the device.
In a further embodiment an environmental coating is disposed on the MMIC. This forgoes the need for hermetic sealing of the microcover. Instead, the MMIC is coated with an environmentally impervious coating at the wafer level prior to attachment of the microcover.
Thus, the packaged MMICs have microwave properties that are independent of placement in modules. In accordance with the invention, metallic, dielectric or magnetic material shapes or features (electromagnetic structures) are printed or lithographically patterned on the inside or outside surfaces of the micro package. Electromagnetic structures are designed to prevent electromagnetic interaction between the MMIC with the external module environment into which the packaged device is mounted. Instead, electromagnetic structures on the microcover are accounted for in the design of the MMIC. They prevent unwanted interactions through the shielding they provide. The result of the packaging method is an invariant die, both in properties and performance. Thus, the need for hermetic sealing of the microcover may be removed since, instead, the MMIC is coated with an environmentally impervious coating prior to attachment of the microcover.
The electromagnetic structures not only prevent unwanted interaction between the MMIC and the external module environment but they also enable MMICs with more gain since the electromagnetic structures can be designed to reduce or control coupling and feedback inside the MMIC.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Reference symbols in the various drawings indicate like elements.